Protection circuits
1. CLIP/Limit
This function is used for preventing dangerous clip signal, which should damage the speakers,
CLIP/Limit monitors the distortion produced by amplifier output, when distortion exceeds 0.5%,
CLIP/Limit will reduce the input signal to ensure signal without distortion (CLIP).
Note: If input signal already has clip or exceeds linearity working range of input circuit, then the
CLIP/Limit is not active!
2. Over-heat protection
If the amplifier works at full loading for a long time, the fans could reach the highest speed. If this
status continue and the temperature rise up to 105, the amplifier will go into over-heat protection
status and the protection indicator (PROT) on the front panel is lit and there's no output.
Therefore,the users are suggested to correctly operate the amplifier, the accepted load should be not
lower than 2 ohm,and the airflow must be abundant and free. The status of no power output is due to
over-heat protection, which usually won't happen if the environment temperature is under 30.
3. VHF protection
If the amplifier output reaches a certain level with large amount of frequencies exceeding 10KHz,
such as MIC feedback noise,then the amplifier may go into VHF protection after 3 seconds, the
protection indicator (PROT) on the front panel will be on and the amplifier will have no output, but it
will be recovered automatically after 10 seconds protection circuit activation. If the output signal does
not change, the VHF protection will continue to be active.
4. Short-circuit protection
All LIBRA series amplifiers have short-circuit protection. This protection make the output transistors
working at safe range. When output is in short-circuit, the protection indicator (PROT) on the front
panel will be lit and the amplifier has no output. The amplifier will be recovered after 10 seconds after
the end of short-circuit removal.
5. AC local power protection
If the AC mains voltage is lower than the minimum allowed working voltage (~160V),the power supply
will be automatically turned off until when the mains voltage returns in regular range.
6. DC protection
If the output signal has large DC voltage (=2.6V), in order to protect the speaker, the DC protection
circuit will be activated. In this case the protection indicator (PROT) on the front panel will be on and
he amplifier will have no output.
Applications
The LIBRA series amplifiers are suitable for live concert, disco, night Club, etc.
Maintenance and troubleshooting
Below are some simple methods to check if the amplifier has been damaged or less:
1. No output
If the signal LED is lit by sufficient signal, then the amplifier shall be fine, please check whether the
speaker(s) output(s) is(are) well connected or not.
2. Low signal output
If the signal LED is lit and clip LED also lit,then please check whether the output connection(s) is(are)
short-circuited or not. If the signal LED is lit,and the protect LED is also lit,then the amplifier shall be
in protection status.There are two possibilities: one maybe over-heat protection,another maybe VHF
protection.Cancelling the input signal, then you can test whether it is VHF protection or not. If the
amplifier chassis temperature is very high,that shall be over-heat protection.If the input voltage is too
low, it may lead to voltage protection, the lowest operating AC voltage is 160V.
3. If the failure is still existing after checking the above suggestions, please return the equipment to the
authorized service agent,it shall be repaired by skilled personnel.
Note: If the amplifier is still in guarantee period,please keep the case in good conditions,don't
disconnect any mechanical parts, otherwise it will not be guaranteed!
10
Professional Audio Equipment
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